﻿namespace Creek.Audio.Codecs
{
    /// <summary>
    /// mu-law decoder
    /// based on code from:
    /// http://hazelware.luggle.com/tutorials/mulawcompression.html
    /// </summary>
    public static class MuLawDecoder
    {
        /// <summary>
        /// only 512 bytes required, so just use a lookup
        /// </summary>
        private static readonly short[] MuLawDecompressTable = new short[256]
        {
             -32124,-31100,-30076,-29052,-28028,-27004,-25980,-24956,
             -23932,-22908,-21884,-20860,-19836,-18812,-17788,-16764,
             -15996,-15484,-14972,-14460,-13948,-13436,-12924,-12412,
             -11900,-11388,-10876,-10364, -9852, -9340, -8828, -8316,
              -7932, -7676, -7420, -7164, -6908, -6652, -6396, -6140,
              -5884, -5628, -5372, -5116, -4860, -4604, -4348, -4092,
              -3900, -3772, -3644, -3516, -3388, -3260, -3132, -3004,
              -2876, -2748, -2620, -2492, -2364, -2236, -2108, -1980,
              -1884, -1820, -1756, -1692, -1628, -1564, -1500, -1436,
              -1372, -1308, -1244, -1180, -1116, -1052,  -988,  -924,
               -876,  -844,  -812,  -780,  -748,  -716,  -684,  -652,
               -620,  -588,  -556,  -524,  -492,  -460,  -428,  -396,
               -372,  -356,  -340,  -324,  -308,  -292,  -276,  -260,
               -244,  -228,  -212,  -196,  -180,  -164,  -148,  -132,
               -120,  -112,  -104,   -96,   -88,   -80,   -72,   -64,
                -56,   -48,   -40,   -32,   -24,   -16,    -8,     -1,
              32124, 31100, 30076, 29052, 28028, 27004, 25980, 24956,
              23932, 22908, 21884, 20860, 19836, 18812, 17788, 16764,
              15996, 15484, 14972, 14460, 13948, 13436, 12924, 12412,
              11900, 11388, 10876, 10364,  9852,  9340,  8828,  8316,
               7932,  7676,  7420,  7164,  6908,  6652,  6396,  6140,
               5884,  5628,  5372,  5116,  4860,  4604,  4348,  4092,
               3900,  3772,  3644,  3516,  3388,  3260,  3132,  3004,
               2876,  2748,  2620,  2492,  2364,  2236,  2108,  1980,
               1884,  1820,  1756,  1692,  1628,  1564,  1500,  1436,
               1372,  1308,  1244,  1180,  1116,  1052,   988,   924,
                876,   844,   812,   780,   748,   716,   684,   652,
                620,   588,   556,   524,   492,   460,   428,   396,
                372,   356,   340,   324,   308,   292,   276,   260,
                244,   228,   212,   196,   180,   164,   148,   132,
                120,   112,   104,    96,    88,    80,    72,    64,
                 56,    48,    40,    32,    24,    16,     8,     0
        };

        /// <summary>
        /// Converts a mu-law encoded byte to a 16 bit linear sample
        /// </summary>
        /// <param name="muLaw">mu-law encoded byte</param>
        /// <returns>Linear sample</returns>
        public static short MuLawToLinearSample(byte muLaw)
        {
            return MuLawDecompressTable[muLaw];
        }

    }
}
